Direct drive ball piston compressor

ABSTRACT

A COMPRESSOR INCLUDING AN ESSENTIALLY SPHEROIDAL PISTON HAVING A BIASED SPHEROIDAL CROWN MEMBER ACTING AS A VALVE AND MATING WITH A CUPOLA SHAPED CYLINDER HEAD.

w. D. GUENTYHER 3,716,310

3 Sheets-Sheet l FIG 4 INVEN-ro @ILL/nm Dy @ummm @GENT DIRECT DRIVE BALL PISTN COMPRESSOR Feb. 13, 1973 Filed Jan.. 2O,` l9'7l wnw@ Feb- 13, 1973 4 w. D. GUENTHER DIRECT DRIVE BALL PISTON COMPRESSOR Filed Jan. 2o, 1971 3 Sheets-Sheet 2 Flea v Fell 13 1973 w. D. GUENTHER vDIRECT DRIVE BALL PISTON COMPRESSOR 3 Sheets-Sheer 3 Filed Jan. 20, 41971 United States Patent C 3,716,310 DIRECT DRIVE BALL PISTN CMPRESSOR William Dieter Guenther, London, Ontario, Canada, assignor to Gun Web Limited, Province of Ontario, Canada Filed llau. 20, 1971, Ser. No. 167,932 Claims priority, application Canada, Mar. 9, 1970,

77,033 Int. Cl. F04b 21/04; F163 1/00 U.S. Cl. 417-552 6 Claims ABSTRACT F THE DISCLQSURE A compressor including an essentially spheroidal piston having a biased spheroidal crown member acting as a valve and mating with a cupola shaped cylinder head.

a significant amount of oil for lubrication.

It has been found that an efficient, light-weight, and physically smaller compressor than conventional compressors can be achieved by using a novel piston configuration essentially spheroidal. The piston head portion of the piston and the rod portion are rigidly connected to one another. Moreover, valves are provided in the head portion for the removal of fluid through it and the profile of the head portion in combination with the cylinder head are such that static fluid disposed between the upper surface of the head portion of the piston and the cylinder head is removed when the piston is at its upper stationary position during the terminal part of the compression stroke.

The invention therefore contemplates a fluid compresor including a power shaft, a cylindrical compression chamber having a cupola shaped cylinder head with apex to create a void, and valve means communicating through said cupola shaped cylinder head with said chamber such that fluid within the compression chamber may be ejected therethrough, and a piston, said piston comprising an ellipsoidal-like shaped head portion with an upper arcuate crown member and a lower truncated skirt portion with upper and lower surfaces and conve-x perimeter, and a rod portion rigidly connected to said skirt portion, said skirt portion having a channel therethrough communicating the upper surface thereof with the lower surface thereof, the convex perimeter corresponding to the loci of the surface of a spheroid having a diameter corresponding to that of the compression chamber such that a circumscribing margin about the convex perimeter is adapted to frictionally engage the Walls of the chamber during reciprocating oscillations of the piston, the arcuate upper crown member biasingly engaging the upper surface of the lower truncated skirt portion to mate therewith but adapted to disassociate from the skirt portion and to expose said channels during intake strokes of said piston, said crown member having its convex surface of ellipsoidal-like shape corresponding to the cupola shape of the cylinder head.

The embodiments of the invention will now be described by way of example, reference being had to the accompanying drawings in which;

FIG. 1 is a cross sectional View of one embodiment 3,716,321 Patented Feb. 13, 1973 ICC of the invention, the piston disposed at the terminal portion of its compression stroke.

FIG. 2 is an end view of the compressor of FIG. 1 partially in section, valve means removed.

FIG. 3 is a cross-section of the chamber and piston, the piston disposed approximately halfway through the intake stroke.

FIG. 4 is identical to FIG. 1, the piston disposed halfway through the compression stroke.

FIG. 5 is a section through the piston of FIG. 1.

FIG. 6 is a comparative cross-section of the head portion of the piston showing two embodiments of ring configurations, and of spring retaining devices.

FIG. 7 is a cross-section along lines 7 7 of FIG. 6.

FIGS. 8, 9 and l0 are representative explanatory drawings of the ring in its various disposed positions during piston cycling with the circumscribing margin indicated as a dash line.

FIG. ll being identical to FIG. 4 but disclosing a coating within the compression chamber.

Referring to FIG. 1 a compressor 20 includes an outer metal housing 21 with appropriate cooling fins 22 and cylindrical compression chamber 23. The compression chamber 23 has a cupola like cylinder head 24 of preferably spherical configuration, with apex (to create a void), the diameter of which is fractionally larger than the corresponding diameter of an upper crown member 33 to be later described. A valve means 25 including a small orifice 26 communicates the apex of the cylinder head 24 to a nipple 27 mounted on the housing 21 for subsequent communication to a reservoir (not shown). Disposed between the nipple 27 and the orifice 26, to provide sealing of the orifice, is a ball 28 biased by a spring means 29.

A piston 31 includes a head portion 32 of truncated spherical shape having an upper crown member 33 of arcuate profile and a lower truncated skirt portion 34 with upper and lower surfaces 15 and 30, and a convex perimeter 35. The lower skirt portion 34 is rigidly connected to one end of a rigid piston rod 36 while the other end of the rod 36 has a protuberance 37 thereon with orifice 38. The orifice 38 accommodates a bearing bushing 39 of suitable type for connection to the throw arm 41 of a powershaft 42. The powershaft 42 is connected to an appropriate prime mover 45 such as an electric motor. The convex perimeter 35 preferably is a circumscribing ring 43 which is mounted on the skirt portion 34 by appropriate means to be described later.

Referring to FIG. 5 the skirt portion 34 is preferably dish shaped accommodating the upper and lower surfaces 15 and 30. Channels 47 communicate through the skirt portion to provide a passage for fluid from its lower surface 30 to its upper surface 15 for reasons which will become apparent. The upper crown member 33 biasly engages the upper surface 15 to sealingly close the channels 47 but is adapted to disassociate from the upper surface 15 during the intake stroke of the piston 31 to thereby openly expose the channels 47 such that fluid can pass through the channels from the lower portion 44 of the compression chamber 23 to the upper portion 46 thereof as more particularly illustrated in FIG. 4. In order to ensure contaminates do not enter the lower portion 44 of the compression chamber 23 a porous plate or screen 50 is provided across the lower extremely of the lower portion of the compression chamber 23. Filtering of the fluid entering the lower portion 44 from the elements is enhanced by the use of a gauze 65 or other suitable filtering media.

Referring to FIG. 6 the biasing of the upper crown member 33 to the upper surface 15 may be accommodated by (referring to the left side of FIG. 6) a flat head screw 48 with underlying spring means 49. Alternatively, it has been found that fabrication during mass production can be simplified if the skirt portion 34 is constructed such that it has a stem 51 projecting from the upper surface coincident with the axis of the piston 31. The spring means 49 is mounted about the stem 51 and washers 52 are placed over the spring means 49. The stem 51 is then peened down in the usual manner to form a rivet type retaining lip 53. (See right hand of FIG. 6).

The operation of the compressor is as follows: The powershaft 42 rotates clockwise and causes the throw arm 41 to move the piston 31 up and down within the compression chamber 23, in the following sequence. Referring to FIGS. l and 2 the piston 31 is disposed within the chamber at the terminal portion of the cornpression stroke (dead stop position). As the powershaft 42 rotates 90 degrees (FIG. 4) the piston 31 is caused to be pulled downward in the chamber 23 while also being tilted to the left as shown. Such tilting results because of the fact that the piston 31 is rigid, that is there is no wrist pin between the head portion 34 and the rod portion 36. The titling is further accommodated by the convex perimeter 35 which describes the locus of the surface of a spheroid whose diameter is equal to that of the compression chamber 23. Referring to FIGS. 8, 9 and 10, the width of the convex perimeter 35, more correctly the length of the chord 54 which subtends the convex perimeter, is such that the degree of tilt is accommodated. In other words, the circumscribing margin of contact 56 between the convex perimeter 35 and the walls of the compression chamber 23 always defines itself on the surface of the convex perimeter 35.

During the intake stroke, the valve means 25 stops shut the orifice 26 and a vacuum exists in the upper portion 46 (that part of the compression chamber between the apex and the piston head 32). As a result fluid in the lower portion 44 of the compression chamber 23 is drawn through the channels 47, into the upper portion 46 as shown. During this stroke, the crown member 33, disassociates itself from the skirt portion 34 to expose the channels 47, and to thereby permit the fluid to flow.

As the powershaft 42 rotates to 180 degrees the piston 31 is drawn further down into the chamber 23 to its full extent. Also it is tilted back into its vertical position. In its dead stop position the spring means 49 urges the crown member 33 back into mating contact with the upper surface 15 to thereby sealingly close the channels 47. As the powershaft moves towards the 270 degree position the piston 31 starts its upward compression stroke tilting to the right (FIG. 4). Fluid which is disposed in the upper portion 46, between the crown member 33 and the cylinder head 24, is forced through the valve means 25 (the ball 28 being displaced as shown in FIG. 4) into the reservoir (not shown). When the 360 degree position is reached the ball 28 is urged back to close the orifice 26. The cycle is then repeated.

Referring in greater detail to the construction of components of the compressor 20, although the ring 43 may be unitary, that is in the form of a solid annulus, in order to accommodate thermal expansion under severe operating conditions, the ring 43 preferably has a lap seam 55 consisting of two correspondingly dependent fingers 57 (FIG. 9) which form a juncture 58 in a plane coincident to the plane perpendicular to the axis of the ring. The fingers 57 expose at the extremities thereof an aperturel 59 to accommodate the expansion and contraction of the ring 43 as a result of thermal change. It has been found that because the width 54 of the ring ring 34 is quite small as compared to its length (perimeter) the fingers 57 may be juxtaposed one to another so that the juncture 58 is for all practical purposes a seal and yet permit a reasonable size aperture 59.

Now referring to FIGS. 8, 9 and 10 it will be seen that the ring 43 is disposed on the lower skirt portion 34 such that the centre of the juncture 58 rests on the pivot axis 61 of the piston head 32. Alternatively, the juncture 58 may be described as being intersected (preferably bisecting the juncture 53) at right angles by the plane which intersects both the axis of the piston rod portion 36 and the axis 61 of rotation of the piston 31. It will be appreciated that if the juncture 58 is not disposed such that the axis of rotation 61 rests on the juncture 58, that loss of sealing across the circumscribng margin of contact 56 between the convex perimeter 35 and the walls of the compression chamber 23 will take place. This can be fully appreciated on careful study of FIGS. 8, 9 and 10.

Referring to FIG. 7, the juncture 58 may be retained in the position such that the pivot axis 61 interescts it, -by an appropriate holding means such as a hold rod 62 disposed between the ring 43 and the lower skirt portion 34.

As will now be appreciated the disposition of the juncture 58 in the manner described insures that no fluid passes between the convex surface 35 and the walls of the cylinder 23, during any portion of the operating cycle of the compressor, especially during the vital compression stroke. Further, in order to improve the sealing contact of the convex surface 35 with the walls of the cylinder 23 it has been found that preferably the composition of the ring 43 should be soft and pliable but wear resistant. It has been found that a suitable material includes tetrafluoride composition such as Teflon, Teflon bronze, glasslilled Teflon and the like. Nevertheless the actual composition for any particular compressor depends upon the wall characteristics of the chamber 23. Teflon and Teflon bronze have been found to be satisfactory where the housing 21 is composed of cast steel and the walls of the chamber 23 have been honed, for example, 16 to 24 microns. Alternatively, if the housing is made of cast zinc, it has been found that by standard copper plating techniques the walls of the compression chamber 23 can be plated with copper, and thereafter plated with a thin coating (0.000 to 0.0001") of nickel which provides a porous and visually dull surface to the walls of the compression chamber 23. When a ring material of Teflon bronze or for high durability of the ring material, glass-filled Teflon is used, excellent wear resistant properties for the ring are achieved. Further it has been found that glass-filled Teflon is an extremely good material for the upper crown member 33.

Now referring again to FIG. 6 the ring 43 and skirt portion 34 may have different profiles. Referring to the left hand portion of lFIG. 6 the ring has an interior profile of that of a groove or channel 71 while the skirt portion has a radially extending tongue 72 which fits into the groove 71. Alternatively, referring to the right hand portion of lFIG. 6, the skirt portion may have a radially extending groove 73 while the ring may have a flat profile 76 as shown. In this embodiment of the ring and skirt portion, the skirt portion 34 has radially extending arms 77 which accommodate the ring 43, the tips of which are arcuate and somewhat recessed from the loci traced yby the surface of a spheroid the convex perimeter 35 is coincident.

It has been found that if the diameter of the spheroid is selected to be one inch, and hence the diameter of the piston head portion, and the length of the piston compression stroke is selected to be three quarters of an inch the compressor disclosed can pump air to a pressure in the neigbourhood of p.s.i. providing of course a sutilciently powerful prime mover 45 is attaced to the powershaft 42. Further, if larger bore compression chambers 23 are used, for example 2" bores, it has been found that the self resilience of the ring 43 is insufficient to constrain the ring 3 against the walls of the compression chamber 23 to ensure good compression. As a result it is desirable to insert between the ring 43 and the skirt portion 34 an encircling spring member (not shown) adapted to urge the ring 43 radially outward against the walls of the chamber 23.

Although the housing of FIG. 4 is satisfactory, it has been found that in order to accommodate mass production in the casting of the housing 21, the housing preferably is provided with a threaded channel 78 communicating with the apex of the compression chamber 23 as shown in FIG. 2.

Into this threaded channel 78 the valve means 25 is threaded. In order to ensure maximum displacement of static air in the upper portion 46 of the compression chamber 23 during the compression stroke, the valve means 25 has its face 79 shaped into cupola to accommodate the upper part of the upper crown member 33 as shown in FIGS. 1, 2, 3 and 4.

Now referring to FIG. 11 the compression chamber 23 has on the interior surface thereof a thin coating 60 of wear resistant material. Preferably, the wear resistant material is a zinc compound. More particularly, the zinc compound is a Zinc anodised coating or what is commonly called anodic film on zinc from electroytes containing one or more anions from the group of glass forming elements-B, Al, Si, or P, plus one or more anions from a group of elements such as Cr, Mn, V or Mo. More particularly sodium silicate-chromate (SSC), sodium silicate-chromate-vanadate (SSCV) and sodium silicatechromate-manganate (SSCMn) electrolytes for anodising zinc have been used. The electrolytic salts and the processes for producing protective coating on articles formed with or coated with zinc and zinc based alloys is commercially available under the trademark Iridizing by Chemical Processing Incorporated of Detroit, Mich., United States of America. Further, these processes have been disclosed in a certain patent by Arnold G. White in Anodic Treatment of Zinc and Zinc-Base Alloys issued in Canada as Pat. No. 605,265 on the 13th day of September 1960 and in the United States of America as Pat. No. .3,011,958 and in the United Kingdom as Pat. No. $776,127. More particularly, such coating having a range of thickness of 0.0075 to 0.0015 inch, particularly 0.0040 inch provides a satisfactory anodic zinc protective coating, 60, on the walls of the zinc alloy, or coated zinc walls of the compression chamber 23 and as a result improves the wear resistance of the chamber 26 particularly from corrosion, erosion, abrasion and also reduces the friction of the tetratluoride composition circumscribing ring 43 on the walls of the compression chamber 23.

lIn order to improve wear-in of the compression ring, with the walls of the chamber 23 a grease may be applied to the Walls of the compression chamber. Such satisfactory grease known as Shell Cyprina No. 3 (GEL) manufactured and sold by the Royal Dutch Shell Oil Company and its subsidiaries has been found satisfactory.

The embodiments of the invention in which an exclusive property or privilege is claimed are dened as follows:

1. A fluid compressor including a power shaft, a compression chamber with a circular cross section having cylindrical walls and a cupola shaped cylinder head with apex to create a void, a channel including a valve means therein communicating through said cupola shaped cylinder head with said chamber such that uid within the compression chamber may be ejected therethrough, and

a piston, said piston comprising an essentially hemispheri cal shaped head portion with an upper arcuate crown member and a lower truncated skirt portion which corresponds to a diametrically symmetrical slice'from a sphere with a diameter corresponding to the diameter of the great circle of the skirt portion to dispose a convex perimeter between upper and lower surfaces; a rod portion rigidly connected to said skirt portion, said skirt portion having a channel therethrough communicating the upper and lower surfaces thereof, the diameter of the great circle of the skirt portion corresponding to that of the compression chamber such that a circumscribing margin about the convex perimeter is a circle adapted to frictionally engage the walls of the chamber during reciprocating oscillations of the piston, a biasing means for biasingly engaging the upper crown member with the upper surface of the lower truncated skirt portion to mate said upper crown member and said truncated skirt portion but adapted to disassociate from the skirt portion and to expose said channel during intake strokes of said piston, said crown member having its convex surface of spheroidal shape corresponding to the cupola shape of the cylinder head and said upper surface of the lower truncated skirt portion being located above said circumscribing margin of the skirt portion so that the surface of the crown member does not frictionally engage the walls of the compression chamber during reciprocating oscillations of the piston.

2. The compressor of claim 1 wherein the piston in its dead stop position at the terminal part of its compression stroke occupies the void created by the cupola shaped cylinder head such that virtually all the static fluid disposable between the cylinder head and the upper crown member is disposed from the void.

3. The compressor of claim 2 wherein the convex perimeter consists of an annular ring of soft, wear-resistant material.

4. The compressor of claim 2 wherein the convex perimeter consists of an annular ring having a lap seam for thermal expansion and contraction thereof, said lap seam including two juxtaposed fingers of the ring, establishing a juncture seal between the fingers, said juncture disposed in a plane coincident to a plane perpendicular to the axis of the piston, while the extremities of the fingers expose an aperture to accommodate linear expansion of the ring, said ring held by a holding means, to retain the juncture of the lap seam such that it is intersected at right angles by the plane which intersects both the axis of the piston rod portion and the axis of rotation of the piston.

5. The piston of claim 4 wherein the axis of rotation of the piston bisects the juncture of the lap seam of the ring.

6. The compressor of claim 5 wherein the ring consists of a tetrauoride composition selected from the class consisting of polytetralluoroethylene, polytetra'uoroethylene-bronze and glass-filled polytetrauoroethylene.

References Cited UNITED STATES PATENTS 1,1091154 9/1914 Thomas 417-552 X 2,779,295 1/ 1957I Manning 417-5 46 2,792,790 5/ 1957 Capps 92-249 X 3,176,595 4/19'65 Schwartz 92-249 X 3,212,41 1 l 0/ 1965 Storms 92`248 3,217,607 11/ 1965 Bitzer 92-249 X FOREIGN PATENTS 1,133,38l8 11/ 1956 France 92-172 ALAN COHAN, Primary Examiner l. C. COHEN, Assistant Examiner U.S. Cl. X.R. 92)--172', 249; 91-422 

